Porous Network Structure Research Articles

Fabrication of Network Spherical α-Al2O3 and Its Application on the Separator of Lithium-Ion Batteries

Ceramic-coated polyolefin separator technology is considered a simple and effective method for the improvement of lithium-ion battery (LIB) safety. However, the characteristics of ceramic powder can adversely affect the surface structure and ion conductivity of the separators. Therefore, it is crucial to develop a ceramic powder that not only improves the thermal stability of the separators but also enhances ion conductivity. Herein, network spherical α-Al2O3 (N-Al2O3) with a multi-dimensional network pore structure was constructed. Furthermore, N-Al2O3 was applied as a coating to one side of polyethylene (PE) separators, resulting in N-Al2O3-PE separators that exhibit superior thermal stability and enhanced wettability with liquid electrolytes. Notably, the N-Al2O3-PE separators demonstrated exceptional ionic conductivity (0.632 mS cm−1), attributed to the internal multi-dimensional network pore structures of N-Al2O3, which facilitated an interconnected and efficient “highway” for the transport of Li+ ions. As a consequence, LiCoO2/Li half batteries equipped with these N-Al2O3-PE separators showcased remarkable rate and cycling performance. Particularly at high current densities, their discharge capacity and capacity retention rate significantly outperformed those of conventional PE separators.

Enhanced flame retardancy of polyurethane foam with alginate-based flame-retardant coating.

Polyurethane (PU) foam is widely used in industrial and civil fields, but it is highly flammable. An eco-friendly flame-retardant coating has been fabricated from sodium alginate (SA) and mica powder, it has been applied to PU foam using a facile direct dip coating method, followed by crosslinking with Ca2+ and modification with polydimethylsiloxane (PDMS), respectively. The original porous network structure is maintained in the coated PU (SMPU) foam with a porosity of 90.51%, and exhibits good thermal stability, hydrophobicity and excellent flexibility. Moreover, the as-prepared SMPU foam exhibits reduced flammability, e.g., the limiting oxygen index (LOI) for combustion of SMPU foam is 30.5%, whereas that for unmodified PU foam is 16%. The SMPU foam also exhibits a self-extinguishing effect without melt dripping and passes UL-94V-0 rating. A significant reduction in the release of heat as well as total smoke and CO2 formation during combustion was noted using cone calorimetry. These improvements in combustion behavior may be ascribed to a physical barrier formed by non-flammable mica powder, SA and PDMS which displays char forming ability. A facile strategy for improvement of the fire safety of PU foam using a green and efficient flame-retardant coating has been demonstrated.

Zero-Tillage Induces Reduced Bio-Efficacy Against Weed Species Amaranthus retroflexus L. Dependent on Atrazine Formulation

Zero-tillage (ZT) is a conservation soil management approach which relies more heavily on herbicide application for weed control than in ploughed soil. Changes in soil management can influence the structure and organisation of pore space in soil, which drives changes in the transport of particulates and dissolved substances. Formulation of pesticides can be used to change the delivery of active ingredients to soil; however, it is currently unknown how changing the formulation of an herbicide can influence the transport properties between ZT vs. ploughing. We investigated the bioefficacy of two formulations of the herbicide atrazine, a pre- and post-emergence herbicide that inhibits photosystem II. Bioefficacy was assessed using physical measures and survival analysis of an early photosynthesis-dependent weed species, Amaranthus retroflexus L., over time, and soil pore network structure was assessed by analysing three-dimensional images produced by X-ray Computed Tomography. Increasing the herbicide application rate generally improved bioefficacy, though it was reduced in soils managed under ZT. Under herbicide-treated ZT samples, survival time was higher, ranging from 13.4 to 18.2 days compared with 12.6 to 15.4 days in ploughed samples, the mean dry plant mass was higher, ranging from 0.5 to 2.5 mg compared with 0.05 to 0.68 mg in ploughed samples, and the mean total plant length was higher, ranging from 1.73 to 12.1 mm compared with 0.2 to 5.45 mm in ploughed samples. Changes in the soil pore network previously demonstrated to be indicators of preferential transport were correlated with measures of bioefficacy, including pore thickness and connectivity density. Reduced atrazine efficacy under ZT is problematic considering the inherent reliance on chemical methods for weed control, we suggest that pursuing formulation strategies to alleviate potential risks of loss via preferential transport may be fruitful.

Preparation of crosslinked lignin-polyacrylamide hydrogel with high resistance to temperature and salinity.

In this study, we innovatively prepared a multifunctional lignin crosslinked polyacrylamide (L-cPAM) hydrogel by a sequential two-step strategy of crosslinking of lignin and crosslinked polyacrylamide (cPAM) followed by the polymerization of cPAM. The hydrogen bonding and crosslinking between the molecular chains of lignin and PAM established a rigid and porous network structure, which provided the L-cPAM hydrogel with excellent mechanical strength, thermal stability, and salinity resistance. A series of lignin dosages (0 to 30 %) were investigated during the crosslinking of lignin and PAM. The results showed that the mechanical strength of the obtained L-cPAM hydrogel could be increased by 53.6 % to 180.71 kPa at a lignin dosage of 15 %. Moreover, the recovery coefficient of the L-cPAM hydrogel after 20 compressions could be maintained at 85.28 %, indicating a strong shape recovery ability. After crosslinking cPAM with a lignin dosage of 15 %, the initial thermal degradation temperature was substantially increased from 150 °C to 181 °C and the shape of the L-cPAM hydrogel could also be maintained for over 60 days in 21× 104 mg L-1 brine at 150 °C. The results suggested that this work provides a new method to construct high-temperature and high-salinity resistant hydrogels using lignin and polyacrylamide.

Effects of cellulose nanofibrils on the mechanical and thermal properties of phase change foams based on polyethylene glycol/cellulose nanofibrils/waterborne polyurethane.

Incorporating phase change materials (PCM) into three-dimensional porous network structures could effectively address the leakage problem. In this study, by investigating the effects of different cellulose nanofibrils (CNF) contents on the mechanical and thermal properties of polyethylene glycol (PEG)/CNF/waterborne polyurethane (WPU) phase change foams, a series of leak-proof, lightweight, and stable PEG/CNF/WPU phase change foams were synthesized. Utilizing CNFs as porous support materials could effectively mitigate the leakage of PCMs. Meanwhile, the incorporation of WPU dispersions leads to the formation of CNFs/WPU composite network structure, which enhances the mechanical strength of the phase change foams and further reduces the leakage of PEG. The morphological, crystallographic, chemical, mechanical, and thermal characteristics of PEG/CNF/WPU phase change foams with varying CNF concentrations were comprehensively assessed using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), mechanical testing, and differential Scanning calorimetry (DSC). The research results indicate that phase change latent heat of PEG/CNF/WPU phase change foam containing 0.8 wt% CNF reached 150.54 J·g-1 and demonstrated superior compressive strength, compressive yield stress, and compressive modulus with a remarkably low leakage rate of just 8.57 % after enduring a 30-day leakage test.

Silver nanoparticle-loaded konjac glucomannan/silk fibroin composite hydrogels for enhanced wound healing.

Hydrogel dressings with good biocompatibility and extracellular matrix mimetic structure are important for the treatment of skin wounds. In this study, antimicrobial silver nanoparticles (Ag NPs) loaded with konjac glucomannan and silk fibroin (KGM/SF) composite hydrogel were used as a dressing for wound healing. The uniform distribution of Ag NPs on the surface of the hydrogels imparts excellent antibacterial properties to KGM/SF composite hydrogels. Furthermore, the incorporation of Ag NPs into KGM/SF composite hydrogels does not induce significant hemolysis, there by meeting the standards for wound dressings and exhibiting favorable biocompatibility. In addition, the SF distribution of complex hydrogel dressings is rich in amino groups, thus providing excellent biocompatibility and comfort. The KGM/SF composite hydrogels possess a porous network structure, which endows them with excellent water retention and the capability to absorb wound exudate. Additionally, this unique structure creates and maintains an optimal moist environment that facilitates wound healing. The KGM/SF composite hydrogel dressing loaded with Ag NPs exhibits excellent hemostatic ability in the skin defect model, thereby facilitating angiogenesis, granulation tissue formation, and collagen accumulation to effectively promote wound healing.

Cross-diffusion waves by cellular automata modeling: Pattern formation in porous media.

Porous earth materials exhibit large-scale deformation patterns, such as deformation bands, which emerge from complex small-scale interactions. This paper introduces a cross-diffusion framework designed to capture these multiscale, multiphysics phenomena, inspired by the study of multi-species chemical systems. A microphysics-enriched continuum approach is developed to accurately predict the formation and evolution of these patterns. Utilizing a cellular automata algorithm for discretizing the porous network structure, the proposed framework achieves substantial computational efficiency in simulating the pattern formation process. This study focuses particularly on a dynamic regime termed "cross-diffusion wave," an instability in porous media where cross-diffusion plays a significant role-a phenomenon experimentally observed in materials like dry snow. The findings demonstrate that external thermodynamic forces can initiate pattern formation in cross-coupled dynamic systems, with the propagation speed of deformation bands primarily governed by cross-diffusion and a specific cross-reaction coefficient. Owing to the universality of thermodynamic force-flux relationships, this study sheds light on a generic framework for pattern formation in cross-coupled multi-constituent reactive systems.

Bio-Based aerogel beads with multistage pore network structure for Cr(VI) removal using ice template method

Bio-Based aerogel beads with multistage pore network structure for Cr(VI) removal using ice template method

A 1.6 mW/cm2 Lactate/O2 Enzymatic Biofuel Cell: Enhanced Power Generation and Energy Harvesting from Human Sweat by 3D Interpenetrating Network Porous Structure CNT-Membranes

Wearable biofuel cells (BFCs) that rely on human sweat for energy harvesting and power generation require highly active enzymes to modify the electrode for biofuel catalysis and oxidation. However, the...

Design a variety of cation exchange hydrogel resins using gamma irradiation to remove hard/scale metal cations from saline water under different circumstances

This study aims to develop a series of cation exchange hydrogel resins via gamma irradiation technique through copolymerizing styrene sodium sulfonate with three acrylamide derivatives (designated as poly(X-co-styrene sodium sulfonate), where X refers to acrylamide (PAASS), methacrylamide (PMASS), and isopropyl acrylamide (PIASS)). The prepared hydrogel resins were characterized and tested for the adsorption removal of hard/scale metal cations (e.g., Ca2+, Mg2+, Ba2+, and Sr2+) from saline water under varying conditions. Results demonstrated that PMASS and PIASS displayed closed porous networks with a significant pH-responsive swelling behavior, increasing from 1.41 to 5.62 g/g in acidic conditions and approximately 41.49 to 45.83 g/g under neutral conditions swelling ratios, while PAASS exhibited an open porous network structure with the stable swelling ratio of around 35 g/g within mild and neutral pH ranges. All hydrogel resins also showed rapid initial adsorption of Ca2+ > Mg2+ > Ba2+ > Sr2+, depending on ionic metal size, with adsorption equilibrium within 3–6 h. Maximum removal was achieved at neutral-basic pH when sulfonate groups were fully deprotonated with a total capacity of about ~ 147–175 mg/g overall mixed metal ions. When exposed to lower concentration solutions, about 87% of metal ions were effectively removed.

Conjugated carbon network mediated - Graphdiyne based Cu2MoS4 homojunction for enhanced charge transfer dynamics

The preparation of stable and environment-friendly catalysts with high photocatalytic performance is of practical significance for the application of photocatalytic hydrogen evolution technology. Graphdiyne has a unique sp and sp2 hybrid structure, making it a potential photocatalyst due to its high surface carrier mobility and porous network structure. In this study, a Cu2MoS4 homojunction composite catalyst with conjugated carbon networks as electron transport channels was prepared by in situ solvothermal growth. Graphdiyne provides an additional pathway for photogenerated electron transfer, improving the efficiency of the interface charge separation. Simultaneously, the built-in electric field at the interface of Cu2MoS4 provides a strong driving force for electron transfer. Owing to the significant visible light absorption and effective multichannel transmission of photogenerated electrons, the Cu2MoS4/graphdiyne composite catalyst exhibited astonishing photocatalytic hydrogen evolution activity (11000 μmol g-1), which is 10 times that of Cu2MoS4 homojunction. Further experimental research and theoretical calculations provided effective evidence for the charge transfer pathway. This work provides a new strategy for constructing efficient hydrogen evolution photocatalysts and regulating the migration of photogenerated electrons.

Glutaric anhydride esterification promotes wheat starch/glutein composite gel interaction: Formation, characterization, and oleogel applications.

This study constructed a composite system with different ratios (100:0, 95:5, 90:10, and 80:20) of glutein compounded with various esterified starch (3% and 6%). The results demonstrated that the esterification process enhanced the viscosity of the starch gel system. Furthermore, the optimal esterification level (3%) facilitated the formation of a dense composite gel network, as observed through microstructure observation. Conversely, elevated esterification levels (6%) resulted in reduced gel system ordering, a loss of crystal structure, and a decline in thermal stability (ΔH reduction). The introduction of glutein promotes interactions within systems, conferring a more continuous structure and positively improving the gel's oil adsorption capacity. NMR images and oil-water distribution curves can verify the ameliorative effect. However, an excessive protein ratio (≥10%) leads to a double decrease in adsorption performance and rheological properties. This porous and lipophilic gel network structure can provide insights for designing solid fats for food products and developing adsorbent templates for chemical industries.

The physicochemical properties of oat starch-fatty acid complexes and application in Lactiplantibacillus plantarum microencapsulation

Oat starch (OS) is the primary component in oat kernels, playing a crucial role in the sensory attributes and functionality of oat products. This study aimed to improve the functional properties of OS by forming oat starch-fatty acid complexes (OS-FAs). Four OS-FAs were prepared using OS and different FAs (stearic acid, palmitic acid, myristic acid, and oleic acid), resulting in OS-S, OS-P, OS-M, and OS-O, respectively. The chemical, functional, and structural properties of these OS-FAs were analyzed and compared with unmodified OS. OS-M was selected for further application in the fabrication of Lactiplantibacillus plantarum (L. plantarum) microcapsules, in combination with sodium alginate and chitosan. The results showed that as the FA carbon chain length and the degree of saturation decreased, the degree of substitution (DS), total resistant starch (RS), water absorption capacity and oil absorption capacity (WAC and OAC), emulsification activity and stability (EA and ES), solubility (SB), and swelling capacity (SC) of the OS-FAs all significantly improved (p < 0.05). The OS-M exhibited the highest DS (0.055), total RS (11.11%), WAC (361.64%), OAC (94.34%), EA (60.87%), ES (61.63%), and best SB (41.22% at 37 °C) and SC (6.13% at 37 °C). The FTIR analysis confirmed that the substitution reactions occurred during complex formation, while the basic starch structure was maintained. XRD and SEM analyses revealed a transformation in crystal morphology from type A to type V, along with a porous network structure and increased specific surface area. Starting from approximately 9.40 log CFU/g, the viability of L. plantarum in OS-M microcapsules was retained at 6.94 and 8.85 log CFU/g in wet and dry capsules, respectively, after simulated gastrointestinal digestion, outperforming microcapsules without OS-M. Additionally, OS-M enhanced L. plantarum protection during 4-week storage at −20 °C (2.91 log CFU/g), 4 °C (8.81 log CFU/g), and 25 °C (6.70 log CFU/g). These findings suggest that modifying OS by forming OS-FA complexes improves its functionality and that OS-FAs hold potential for use in probiotic encapsulation to enhance bacterial viability.

Preparation of Hydrogels of Methacrylamide with Mono and Dicarboxylic Acids: Investigation of Their Swelling Behavior

Methacrylamide (MAAm) hydrogels were synthesized with mono- (crotonic acid, CrA) and dicarboxylic (maleic acid, MAA) acids via radical copolymerization, utilizing potassium persulfate (KPS) as the initiator and methylenebisacrylamide (MBAAm) as the crosslinker. The swelling behavior of the resulting hydrogels was systematically investigated, with particular focus on the effects of monomer ratio, initiator and crosslinker concentrations, as well as polymerization temperature. These parameters were optimized to maximize the swelling ratio. For poly(MAAm/CrA) hydrogels, the formulation containing 85/15 MAAm/CrA (mol/mol), 2 mol% KPS, 1 mol% MBAAm, and synthesized at 55 °C exhibited the highest swelling capacity (480%) in distilled water. In contrast, for poly(MAAm/MAA) hydrogels, the composition of 75/25 MAAm/MAA (mol/mol) with 1 mol% KPS, 1 mol% MBAAm, and polymerized at 55 °C showed a maximum swelling of 1100%. Further investigations explored the influence of pH, temperature, and electrolyte concentration and type on the swelling properties of the hydrogels prepared under optimized conditions. Both hydrogels demonstrated peak swelling behavior at pH 7, with their swelling profiles varying in response to changes in temperature, electrolyte concentration, and electrolyte type. Swelling kinetics studies revealed that the MAAm/CrA hydrogel exhibited Fickian diffusion in distilled water at room temperature, while the MAAm/MAA hydrogel followed a non-Fickian diffusion mechanism. Scanning electron microscopy (SEM) analysis indicated that the hydrogels synthesized under optimal conditions possessed a porous and well-organized network structure.

Micro-Nanofiber Three-Dimensional Antibacterial Sponge with Wetting/Pore Dual Gradient for Rapid Liquid Infiltration and Uniform Retention in Diapers.

The core layer of disposable diapers typically contains a blend of superabsorbent polymer (SAP) and pulp, resulting in slow liquid absorption, layer separation, reverse osmosis, and potential skin issues owing to the addition of antibacterial agents to the surface layer. Therefore, a core layer with rapid liquid absorption, uniform retention, and antibacterial properties must be developed to improve wearer comfort. In this study, a three-dimensional network porous structure for the core layer of a disposable diaper was prepared by solution blow spinning (SBS). This structure comprised a superabsorbent fiber (SAF) and hydrolyzed polyacrylonitrile (HPAN) micro/nanofibers with a dual gradient in wetting/pore size. Progressively increasing the SAF content in each layer to incrementally increase wettability and controlling fiber diameter, a gradient pore structure with sizes of approximately 30 μm-16 μm-7 μm was formed. This design exhibited rapid infiltration capability, reducing the third liquid infiltration time by 13 s compared to those of commercial core layers while reducing reverse osmosis by 1.4 g, and the liquid absorption and retention rates are 47.7 times and 46.1 times, respectively, which is 1.6 times higher than those of commercial diapers. In addition, incorporating a natural antibacterial agent, ε-poly-l-lysine hydrochloride (ε-PLH), into the core layer resulted in an antibacterial rate exceeding 99.99% without direct contact with the skin; water transport capacity tests confirmed faster liquid infiltration speed, uniform absorption, and no fault formation.

Low-temperature reduction of NOx with NH3 using a hybrid system of non-thermal plasma-LaMn0.9CO0.1O3 perovskite nanocatalyst

The catalytic reduction of NOx at low temperatures presents a significant challenge, which can potentially be overcome by integrating plasma into the process. Porous perovskites emerge as promising catalysts for plasma-assisted NOx removal. In this study, perovskite catalysts LaMnO3 and LaMn0.9Co0.1O3 were synthesized using the auto-combustion sol-gel method with different fuels and subsequently evaluated for their efficiency in plasma-catalytic NOx removal in the presence of NH3. Analyses including XRD, BET, FESEM, TEM, FTIR, DRS, and TGA indicated that while the samples exhibited similar crystal sizes, they displayed varying levels of defects. Notably, the LaMn0.9Co0.1O3 catalyst synthesized with citric acid as the fuel (designated as LMC-Ci) demonstrated a highly porous and homogenous network structure, characterized by cubic-spherical particles measuring 20–30 nm, as corroborated by the XRD data. The co-substitution of cobalt in LaMnO3 enhanced light absorption, enabling the catalyst to effectively utilize ultraviolet photons produced by the plasma. Among the evaluated catalysts, LMC-Ci achieved the highest activity, resulting in a 98 % removal rate of NOx. The study further examined the influence of operational parameters, including discharge time, temperature, space velocity, and specific input energy, on the performance of the selected catalyst, revealing that plasma presence significantly reduced the operating temperature to 80 °C.

Preparation of strong, tough and highly ion-conductive nanocellulose hydrogels based on freeze–thaw cycles: performance evaluation under different freezing temperatures

Abstract Rapid and effective preparation of hydrogels with excellent properties by cyclic freezing–thawing has remained an enormous challenge as hydrogels prepared using traditional freeze–thaw methods demonstrate poor, unstable and unalterable mechanical properties. In this study, an innovative method was introduced to develop a nanocellulose hydrogel with excellent properties via cyclic freezing–thawing and ionic cross-linking, and various methods were used to characterise the structure and properties of the hydrogel. The results showed that hydrogen and ester bonds existed in the soy hull nanocellulose–sodium alginate–calcium chloride (SHNC/SA/Ca2+) hydrogel and that the internal structure of the hydrogel changed from a lamellar to three-dimensional network structure owing to low temperature, increasing the cross-linking density of SHNC and SA and enhancing the mechanical strength of the hydrogel. Meanwhile, the SHNC/SA/Ca2+-4 hydrogel demonstrated excellent elongation (804 %), viscoelasticity (storage modulus = 89.6 kPa), mechanical strength (tensile strength = 0.59 MPa, compressive strength = 1.52 MPa), ionic conductivity (3.84 S/m), transparency (54 %), anti-ultraviolet properties and fatigue resistance. The simple preparation process, excellent performance and three-dimensional porous network structure of the nanocellulose hydrogel offer broad application prospects in many fields.

Electrospun polyvinyl alcohol/chitosan nanofibers modified with carbon nanotubes and sliver particles for electrochemical sensor application

Polyvinyl alcohol (PVA)/chitosan (CS) nanofibers modified with carbon nanotubes (CNT) and silver (Ag) particles are electrospun onto a graphite plate (GP) substrate to form the PVA-CS-CNT-Ag/GP electrode for electrochemical sensor application. Microstructure characterization demonstrates that PVA-CS nanofibers exhibit a loose and porous network structure, significantly improving the effective reaction surface area. Electrochemical measurements show the PVA-CS-CNT-Ag/GP electrode exhibits the limit of detection of 23.2 μM, the linear range of 65–176,460 μM and the sensitivity of 3.3945 μA cm−2 mM−1. Anti-interference test results show that the sensor has high selectivity towards H2O2. Stability test results indicate that the sensor exhibits good stability, as evidenced by the response current of 83.94 % after a period of 30 days. Simulation calculations indicate that PVA-CS-CNT-Ag exhibits lower interfacial energy (−2.3293 eV) compared to PVA-CS-CNT (−0.3674 eV) and PVA-CS-Ag (−0.7646 eV), smaller band gap (0.318 eV) compared to PVA-CS (3.640 eV), higher density of states at Fermi level (14.7332 electrons/eV) than others. Experimental measurements and simulation calculations indicate that PVA-CS-CNT-Ag electrospun nanofibers exhibit promising potential as an electroactive material for the electrochemical detection of H2O2.

Breaking the 500-Dalton Rule of Transdermal Drug Delivery by Locally Stretching Skin with Porous Micropost Array

Transdermal drug administration has been attracting attention for its variety of advantages, such as elimination of pain and its minimal invasiveness. However, the efficacy of transdermal drug delivery is limited by the stratum corneum, the outermost layer of the skin. The permeable molecular size through the stratum corneum is known to be roughly below 500 Da, which is known as the 500-Da rule in the area of transdermal drug delivery (1). Various techniques have been explored to enhance transdermal permeation, including, microneedles, thermal ablation, microdermabrasion, electroporation and cavitational ultrasound (2). Among them, microneedles, in particular, have been extensively studied and tested for clinical use.In this work, we discovered that the blunt frustoconical-shaped microneedles or microposts can increase the permeability of skin by locally stretching the stratum corneum without penetration (Figure 1a). Through testing with various molecular sizes, we successfully demonstrated that molecules with a size of approximately up to 10 kDa can be injected. Due to its minimally invasive nature, we propose this as an alternative noninvasive approach to conventional microneedle transdermal drug delivery.Porous frustoconical microneedle arrays (PMN) were fabricated using methacrylic-based materials with microscopic porous network structures (Figure 1b), based on our group’s protocol (3). Ions and molecules can pass through the network by applying weak electric field to introduce electrophoresis and electroosmosis. Using the developed micropost arrays, we conducted the following experiments. Firstly, we measured the transdermal electrical resistance of a pig skin with the PMN array pressed onto the skin. A non-penetrating frustoconical PMN array was found to reduce the transdermal resistance to a similar level as the sharp PMN array that physically penetrates stratum corneum, indicating that local stretching of the stratum corneum can enhance ion and molecular permeability of the skin even without penetration. Secondly, we applied a weak electric field to the PMN array to induce electroosmotic flow (EOF) inside the porous network and measured the drug permeabilities through pig skin using fluorescent-labeled drug molecules with different molecular sizes (Figure 1c). The amount of the permeated drug was evaluated by enzymatically degrading the skin samples and measuring its fluorescent intensity. We found that drug molecules could permeate only when the skin was stretched with the PMN array and EOF was present simultaneously. The synergy between the extension of the stratum corneum and EOF promotion enables the minimally invasive transdermal drug delivery that is even less invasive than the conventional sharp microneedles. We quantitatively confirmed that at least 10-kDa molecules can permeate through the stratum corneum with our developed frustoconical PMN array.In summary, we developed a porous micropost array that can locally stretch stratum corneum to enhance chemical and drug transdermal permeability. By measuring the electric resistance and using fluorescent imaging, we confirmed that drug molecules with a size of approximately 10 kDa can be delivered using a porous micropost array without penetrating the stratum corneum. Our approach of using micropost array significantly widens the window of possible drug molecular sizes for transdermal applications.Figure (a) Frustoconical microposts locally stretch the stratum corneum and increase drug permeability through the skin. Electroosmotic flow pumps out the drug molecules loaded in the porous structure. (b) Fabricated porous micropost array. (c) Fluorescent image of 10-kDa FITC-Dextran molecules permeating through the stratum corneum.References Bos JD & Meinardi MMHM (2000) The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Exp Dermatol 9(3):165-169. Prausnitz MR & Langer R (2008) Transdermal drug delivery. Nat Biotechnol 26(11):1261-1268. Terutsuki D, Segawa R, Kusama S, Abe H, & Nishizawa M (2023) Frustoconical porous microneedle for electroosmotic transdermal drug delivery. J Control Release 354:694-700. Figure 1

Synthesis of Super-High-Viscosity Poly-γ-Glutamic Acid by pgdS-Deficient Strain of Bacillus licheniformis and Its Application in Microalgae Harvesting.

Poly-γ-glutamic acid (γ-PGA) is a natural polymer whose molecular weight and viscosity are critical for its application in various fields. However, research on super-high-molecular-weight or -viscosity γ-PGA is limited. In this study, the pgdS gene in Bacillus licheniformis WX-02 was knocked out using homologous recombination, and the batch fermentation performances of the recombinant strain WX-ΔpgdS were compared to those of WX-02. Nitrate accumulation was observed in the early fermentation stages of WX-ΔpgdS, and gene transcription analysis and cell morphology observations revealed that nitrite accumulation was caused by oxygen limitation due to cell aggregation. When the aeration and agitation rates were increased to 2.5 vvm and 600 r/min, respectively, and citrate was used as a precursor, nitrite accumulation was alleviated in WX-ΔpgdS fermentation broth, while γ-PGA yield and broth viscosity reached 17.3 g/L and 4988 mPa·s. Scanning electron microscopy (SEM) showed that the γ-PGA produced by WX-ΔpgdS exhibited a three-dimensional porous network structure. At a γ-PGA concentration of 5 mg/L, the fermentation broth of WX-ΔpgdS achieved a flocculation efficiency of 95.7% after 30 min of microalgae settling. These findings demonstrate that pgdS knockout results in super-high-viscosity γ-PGA, positioning it as an eco-friendly and cost-effective biocoagulant for microalgae harvesting.